Update README

README.md

@@ -1,17 +1,137 @@
 # RootMyTV
 
-RootMyTV is a "remote" root exploit chain, and Jailbreak, for LG WebOS smart TVs.
+RootMyTV is a "remote" root exploit chain, and Jailbreak, for LG webOS smart TVs.
 
 All you need is an internet-connected smart TV, and a TV remote (or alternatively, an Arduino and an IR LED!).
 
 # How it works
 
 In summary, we use a chain of exploits to get persistent root code execution.
-As root, we install the [WebOS Homebrew Channel](https://github.com/DavidBuchanan314/webos-homebrew-channel) app, and disable various
+As root, we install the [webOS Homebrew Channel](https://github.com/webosbrew/webos-homebrew-channel) app, and disable various
 security/sandboxing/jailing anti-features.
 
 ## Rooting
 
+### Background
+
+webOS, as the name suggests, is a Smart TV operating system mostly based on web
+technologies. Applications, both system and external are either run in a
+stripped down web browser ("WebAppMgr") or in Qt QML runtime. Almost all system
+and external applications run in chroot-based jails as an additional security
+layer.
+
+"Web apps", outside of standard web technologies, also get access to an API for
+communicating with "Luna Service Bus". This is a bus, similar to D-Bus, used to
+exchange messages and provide various services across different security
+domains. Bus clients can expose some RPC methods to other applications
+(identified by URIs `luna://service-name/prefix-maybe/method-name`) which accept
+JSON object message as their call parameters, and then can return one or many
+messages. (depending on the call being "subscribable" or not)
+
+While Luna bus seems to have extensive ACL handling, considering the history of
+webOS IP transfers, seems like not many engineers fully understand its
+capabilities. Part of the bus is marked as "private", which is only accessible
+by certain system applications, while most of the other calls are "public" and
+can be accessed by all apps.
+
+Unexpectedly, one of the "public" services exposed on a bus is "LunaDownloadMgr"
+which provides a convenient API for file download, progress tracking, etc...
+Said service has been researched in the past and an identity confusion bug
+leading to an arbitrary unjailed root file write vulnerability has been
+[publicly documented](https://blog.recurity-labs.com/2021-02-03/webOS_Pt1.html).
+
+This in of itself was not very helpful in production hardware, thus we needed to
+find a way of calling an arbitrary Luna service from an application with
+`com.webos.` / `com.palm.` / `com.lge.` application ID.
+
+### Step #0 - Getting in (stage1.html)
+
+In order to gain initial programmatic control of the TV user interface an
+interface of "LG Connect Apps" can be used. Its protocol called "SSAP" is a
+simple websocket-based RPC mechanism that can be used to indirectly interact
+with Luna Service bus and has been extensively documented in various
+home-automation related contexts.  We use that to launch a vulnerable system
+application which is not easily accessible with plain user interaction.
+
+#### Step #0.1 - Escaping the origins
+
+SSAP API is meant to be used from an external mobile app. For the sake of
+simplicity, though, we wanted to serve our exploit as a web page. This lead us
+to notice, that, understandably, SSAP server explicitly rejects any connections
+from HTTP origins. However, there was an additional exception from that rule,
+and seemingly authors wanted to allow file:// origins, which present themselves
+to the server as `null`. Turns out there's one other origin that can be used
+that is also reprted as `null` and that is `data:` URIs.
+
+In order to exploit this, we've created a minimal WebSocket API proxy
+implementation that opens a hidden iframe with a javascript payload (which is
+now running in a `data:`/`null` origin) and exchanges the messages with the main
+browser frame. This has been released as [a separate
+library](https://github.com/Informatic/webos-ssap-web).
+
+#### Step #0.2 - General Data Protocol Redirection
+
+There's a minor problem with establishing the connection with SSAP websocket
+server. While we all believe in utter chaos, we don't feel very comfortable with
+serving our exploit over plain HTTP, which would be the only way of avoiding
+Mixed Content prevention policies. (by default https origins are not allowed to
+communicate with plain http endpoints)
+
+While [some newer Chromium versions](https://chromium.googlesource.com/chromium/src.git/+/130ee686fa00b617bfc001ceb3bb49782da2cb4e)
+do allow Mixed Content communication with `localhost`, that was not the case
+when Chromium 38 was released (used in webOS 3.x). Thankfully, it seems like the
+system browser on webOS 3.x is also vulnerable to something that has been
+considered a security issue in most browsers for a while now - navigation to
+`data:` URIs. Thus, when applicable, our exploits attempts to open itself as a
+`data:` base64-encoded URI. This makes our browser no longer consider the origin
+being secure, and we can again access the plain-http WebSocket server.
+
+### Step #1 - Social login escape (stage1.html)
+
+Having some initial programmatic control of the TV via SSAP we can execute any
+application present on the TV. All cross-application launches can contain an
+extra JSON object called `launchParams`. This is used to eg. open a system
+browser with specific link open, or launch a predetermined YouTube video. Turns
+out this functionality is also used to select which social website to use in
+`com.webos.app.facebooklogin`, which is the older sibling of
+`com.webos.app.iot-thirdparty-login` used in initial exploit, present on all
+webOS versions up until (at least) 3.x.
+
+When launching social login via LG Account Management this application accepts
+an argument called `server`. This turns out to be a part of URL that "web app"
+browser is navigated to. Thus, using properly prepared `launchParams` we are
+able to open an arbitrary web page (with the only requirement being it served
+over `https`) running as a system app that is considered by `LunaDownloadMgr`
+a "system" app.
+
+### Step #2 - Download All The Things
+
+Since we are already running as a system application, we can download files
+(securely over https!) into arbitrary unjailed filesystem locations as root.
+
+We use that to download following files:
+
+* `stage3.sh` →
+  `/media/cryptofs/apps/usr/palm/services/com.palmdts.devmode.service/start-devmode.sh` -
+  this is the script executed at startup by `/etc/init/devmode.conf` as root,
+  in order to run developer mode jailed SSH daemon.
+* `hbchannel.ipk` → `/media/internal/downloads/hbchannel.ipk` - since our end
+  goal is intalling the Homebrew Channel app, we can also just download it
+  during the earlier stages of an exploit and confirm it's actually downloaded.
+* `devmode_enabled` → `/var/luna/preferences/devmode_enabled` - this is the flag
+  checked before running `start-devmode.sh` script, and is just a dummy file.
+
+### Step #3 - Homebrew Channel Deployment
+
+`stage3.sh` script is a minimal tool that, after opening an emergency telnet
+shell and removing itself (in case something goes wrong and the user needs to
+reboot a TV - script keeps running but will no longer be executed on next
+startup), installs the homebrew channel app via standard devmode service calls
+and elevates its service to run unjailed as root as well.
+
+
+# Legacy
+
 "LG ThinQ Login" is a privileged app, which is used to sign in to various "smart" services.
 If we use the option to sign in with an Amazon account, we can click web links, and
 ultimately end up on google.com. From there, we can search and navigate to [RootMy.TV](https://rootmy.tv),
@@ -27,7 +147,7 @@ every subsequent boot, our code in `start-devmode.sh` script gets run as root.
 
 ## Jailbreaking
 
-Normally, the only way to run your own code on WebOS is to [enable Developer Mode](https://webostv.developer.lge.com/develop/app-test),
+Normally, the only way to run your own code on webOS is to [enable Developer Mode](https://webostv.developer.lge.com/develop/app-test),
 which is an officially supported feature. There are four big problems with LG's
 Developer Mode:
 
@@ -51,9 +171,11 @@ The `start-devmode.sh` startup script contains code to overcome these limitation
 
 # Homebrew Channel
 
-To take full advantage of these new features, I created the "[WebOS Homebrew Channel](https://github.com/DavidBuchanan314/webos-homebrew-channel)" app.
+To take full advantage of these new features, we created the "[webOS Homebrew Channel](https://github.com/DavidBuchanan314/webos-homebrew-channel)" app.
 This app allows users and developers to easily "sideload" their own apps.
 
-It also
+It also provides some Luna IPC services which may be useful for jailbroken app development, including
-provides some Luna IPC services which may be useful for jailbroken app development, including
+the ability to run shell commands as root. We also provide a user-friendly
-the ability to run shell commands as root.
+interface to manage various configuration options, like locking software update
+nagging, early boot user scripts with some fallback in case of system crashes
+or exposing root SSH daemon.